Telegraph system



.April 191927 H. W. oNElLL TELEGRAPH SYSTEM Y Filed Aug. 8. 1925 A/AZ III-II' 4 Sheets-Sheet 1 fai) H. W, ONEILL TELEGRAPH SYSTEM April 19, 192'). 1,625,495

Filed Aug. a. 1925 4 sheets-sheget 2 Apr 19 2 H. w. ONEILI.

TELEGRAPH SYSTEM Filed Aug. 8. 1925 4 Sheets-Sheet 5 @mi ....i... hf IIV.. n m m m *QM 88 F T. m hm' D n m n n n ll @ull www um U .v k. VIL NND um NHG .April 19,1927.

. H. w. ONEILL TELEGRAPH SYSTEM Filed Aue.. 8 1925 4 Sheets-Sheet 4 Patented Apr. 19, 1927.

UNETED STATES 'Partnr orrics.

HENRY W. ONEILL, OF ELMHURST, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEGRAPH SYSTEM.

appueauon mea August s, 1925. semi No. 48,949.

This invention relates to telegraph systems, and more especially to telegraph systems wherein alternating currents of audio frequency are employed for signalling.

An object of the invention is to provide an efficient and highly economical alternating current telegraph system, utilizing currents of audio frequency.

A feature of the invention relates to an alternating current telegraph system in association with circuits where relatively low potential levels may not be exceeded, and

wherein special relays are employed for directly converting alternating current telegraph signals ino continuous current signals. i

Another feature of the invention relates to a telegraph system employing carrier currents within the voice frequency range, in conjunction with so-called acceleration type relays as detectors and filters.

rrfur'her feature relates to an alternating current telegraph system wherein short-circuiting vibrators are employed as sources of alternating currents.

r-in additionel featureirelates to current producing devices which may no-rmally be inert but automatically rendered responsive to the transmission of signals.

A still further feature relates to an arrangement for employing guard or pilot current with a telegraph line during nontransmission periods.

Another feature relates to a high-speed direct current telegraph system which is composited with, and rendered operable by ,he present alternating current system.

Referring to the drawing, Fig. l shows loop circuits comprising sending and receiving` legs S and-R terminating in a telegraph switchboard TS, at a central office.

Fig. 2 shows other portions of the switching equipment which includes apparatus for monitoring and commuicating from the switchboard.

F 3 to the left of the broken line shows a number of ltransmitting channels T1, T2, ec., with associated alternating currentcircuits. This portion of the figure also shows in detail a first receiving channel RC1, and a second similar receiving channel RC2. The portion of Fig. 3 tothe right of the broken line represents transmitting and receiving equipment at a, distant Dse which equipA ment may be similar to that shown in Figs. l and 2, in the left-hand portion of Fig.` 3 and in Fig. 6.

Fig. 4 shows the manner in which a two conductor line may be duplexed, by means of balancing coils, and composited with a high-speed ground return Morse duplex system. I y

Fig. 5 shows the manner in Awhich a metallic Morse system may be combined with the duplex line of Fig. l in substitution of the grounded Morse equipment; while Fig. G shows` in abbreviated form equipment which may correspond with the equipment of Figs. l and 2.

Figs. 1,2 and 3 'of the drawing when arranged with Fig. 2 above Fig. l, and Fig. 3 to the right of Fig. l, show in sufficient detail such portions of a telegraph system as may be necessary to a clear understanding of one formof carrying out the invention.

For convenience of description, lthe system may be divided` into an alternating current portion and a direct current portion. The alternating current circuits, for transmitting, comprise carrier current supply sources which may be formed of vibrators preferably of the short-circuiting type, as shown, with means for contro-lling the application of such currents to a main line. For receiving such currents, suitable relays, preferably of acceleration type, as shown, serve as detectors and filtersin. separating the several carrier currents according to frequency, and in translating them into direct current signals. The direct current circuits currents at a receiving point may be reperform twor main functions. The outgoing carrier currents may be controlled by the ordinary Morse telegraph signals from a transmitting device, while in turn` the Morse signals resulting from the incoming carrier peated into a loop, or oher telegraph circuit by means of relays of the acceleration ctc. serve to join a plurality of Morse tch graph equipmens with the main lines.

El hh ,llorse extension may comprise a sending leg and a receiving;v leg. ller example. the extensions shown in detail in Fig. l, comprise sending` lei; lill and receiving leg' 10Q. Similarly, the extensions shown in Fin'. (t comprise a sending legi' ltll and receiving; legi' 10i. lt will be understood that other lllcrsc extensions similar to 10i and lili?. may be provided as required. The. switching devices` (lli il) provide that the circuitsinay be conditioned tor `either tull duplex or :tor hall" duplex workingl at a terminal or substation as will presently appear. Associated with cach line there is a conveir tional monitoring' and supervisory control. circuit also shown `in Fig.

In association with each ot' the sending' and receiving legs, there is respective-ly pro vided ai transmitting" and a receiving' channel. Each transmitting channel supplied with carrier current ot a particular trc- (juency. The carrier frequencies .are so chosen as to be odd n'inltiples oit a basic t're quency which tor convenience will referred to as a #frequency f1. The lowest treqnency'employed in the present system is the tiith multiple oit this frequency and will thereilore be referred to as a frequency f5. Each carrier frequency is allotted a range ot f f 2 and therefore is separated 'from the limits of' the two adjacent frequencies by a 'frequency corresponding' to the frequency f1 cycles above and f" cycles below its own nominal frequency.

4The carrier 'frequency generatinpY means comprises shortfcircuitingr vibrators 311, 312, etc., which may be mechanically tuned. as well as electrically tuned with a circuit comprising the windings ot a transformer such as the unit 2301.. The primary winding of this transformer may be tuned by means o't ai condenser B2i, while thc secondary may be tuned `by a condenser 383. Ordinarily, no additional liltering equipment in the carrier generator circuit will be necessary, since it is an inherent characteristic ot short-cireuiting vibrators that the resulting wave torni is comparatively smooth and tree 'from sharp current etl'ecter lndividual to each receiving; channel RC1, RC2, ete, is a receiving relay 30%, 30e. etc. These relays are preferably of the socallcd Ltaccelenationi type such'as shown and described in U, S. patent granted to lil. W. oNeiu. Nm: 2:1, ieee. Leoncio.

As described in the above mentioned patentl the acceleration type relays consist ot' an armature capabli` ol vibrating' adyacent the poles ot' an electromagnet which is adapted to be energized b v alteriultingcurrent'. They armature carries a sealed cnaniber wherein a so-called loose7 contact assembly provided. The armature is further-nunc adapted to be mechanicallyY tuned to any dc sired frequency.. lllhcn a suitable alternatiinr current is sent through the windings ol such a relay, the resulting` vibratile etl'ect ot the armature causes the normally closed contacts within the sealed chamber to separate. while on cessation ol the current the contacts may close. ln addition to being tuned mechanically', these relays may also be tuned electrically by means ot condensers as condenser 530.5. .llue to the extreme sensitiveness and selectivity oit the receivingl relaysl` a j unparatively large number ot' dill'ercnt carrier trecuencies may be transmitted over a main line, without exceeding the usual voltage levels permissible in the circuits oit a telephone plant. Furthermore these receiving' relays are substantially nnatlected by inductive surges and will not translate sie'- nals other than those t'ormed by impulses composed ol a stream or succession oit waves ot the particular Frequency to which the rcceiving relay may7 be tuned. Because olthis latter feature, the receiving relays permit the superposing:y ot alternating currents over circuits operated with direct currents, either on the metallic lvlorsej or the ground return lllorse principles.

le direct current polar duplex circuit is toi-med by a sending relay 100 and a break relay 10E), both oil polarized type. ',lhe lett windings ot these relays connect to an artitieial line represented by a resistance 201i, while thc right windings connect over the loop circuit l0l, to positively-poled `srrounded battery. The apex ot the duplex circuit, formed by the junction oit the wind ings in the dillferentially connected current meter 110, is connected by way of a jack 202 to negatively polcd battery. In conventional manner, the `greater energy through the right. or line windings oit the relays '100 and 109 normally stresses the armatures ot these relays to their marking contact stops` as shown. The reference characters S and M have. tor conveniencel` been employed to respectively indicate the spacing and marking' contacts of the yarions line-controlled relays oit this system.

In the present system the equipment at: the East ollice shown to the rigzjlit ot the broken line ot Fig. 3 may be in diiplicate ot the equipment at the lliest otiice, where the circuits are fully shown in diagrammatic torni. lherelore, in avoiding unnecessary duplication, the rectangle 301 and circle STl may be umlcrstood as inclosing` receiving equipment under control ot the transmitt l equipment lormcijl ol Vl.11 (Fig. il). and the transmitting portion ot Figs, l and i?. yThis receivingr cquijnnent may correspond with that formed by the relay S30-l and the receiving portion of the equipment ot Figs. 'l and Q. This transmitting and receiving equipment terms a first channel over the cast line station. y 1WL mayr -spectively connect to the correcircuit EL.` Over this linea second trequency channel is formed by transmitting equipment T2 and a portion of 6 Werl;- ing into receiving equipment Within 302 and 872. A West line lVL has a lirst frequency channel formed oftransmiting equii'nnents 367, 377, Working into receiving equipment formed of relay 304 and the receiving portion ot Figs. 1 and 2, While a secondft'requency channel over this line, comprises transmitting equinnent 308, 378. Working into receiving equipment. con'iprising relays 306 and the receiving portion of Fig. 0.

lllithin a rectangle 323 is shown transmitting pilot equipment tor the east line EL which controls receiving equipment which may be assumed as present at 303. F or the West line VIL, pilot transmitting equipment 373 serves for cont-rol of .receiving equipment 353. The receiving equipment at 30?) may correspond with that at 353, vvhile the transmitting equipment at 373 may corre spend With the transmitting equipment at 323. Y

From the foregoing it will be clear that the circuit EL, with the circuit lVL, may constitute a so-called four-Wire system, in which a circuit of tvvo conductors may carry transmision for a plurality otchannels in one direction, While a second tivofvvire circuit serves reciprocally for carrying transmission tor a plurality of channels in the opposite direction.

ln taking advantage of the inherent sensitivity and selective characteristics of the present acceleration7 type relays, a single two-Wire line circuit may, When desirable, be` employed in substitution o1- a four-wire circuit system for carrying impulses for channels in which the transmission may be in opposite directions. To render this readily understood in connection with the present disclosure, the equipment of Fig. 4 may be'substituted for the equipment at the East For this purpose, line EL andline spondingly indicated conductors of a balancing coil 401 Which forms a metallic' duplex arrangement for a two-Wire main line ML. A balancing coil 402 at the opposite end oit this line may, in turn, b auch to a. second tour-Wire line section, orthe conductors'ot the receiving side and those of the transmitting side may be respectively joined to receiving and transmitting equipments as present at the East stationv of Fig. 3.

The characteristic oi the present acceleration type relays concerning their immunity to relatively slon7 moving current impulses, Which characterize the highest speeds ot direct current telegraphs as compared With the order of the frequencies employed in the. alternating current portions ot the present system, render it possible to composite' the line ML with direct current telegraphs without employing the usual inductance and capacity units for smoothing the direct current impulses. In turn, the ordinary direct current telegraphic devices are immune to the low potential high frequency alternating currents of the present system, therefore, ground ret-urn telegraph system as shown, may also be employed with the line ML. As Well understood, in the telegraph art the, reactances employed for smoothing the impulses in former composited circuits ati'ect to a. marked degree the speed at which signalling' may be carried on over such direct current telegraph circuits. The features of the present system as already pointed out whereby the impulse smoothing reactances may be dispensed with, is of importance from the standpoint of reduced cost tor equipment, and affording a gain in message capacity ot a channel due to the higher speeds of sending which may be employed over the direct current channels.

r)The foregoing 'features relative to composited circuits also apply to superimposed direct current Working on the metallic Morse basis. For this, the arrangement of Fig. 5 may be substituted it'or the arrangement ot' Fig. 4, thereby providing` that in addition to simultaneous east and West Working oi alternating current channels over the line sectionML, a metallic or two-Wire direct current duplex telegraph system may also be operated over this line.

In a. more detailed description et this system, let it be assumed vthata lrey 201 is operated to its alternate position, a battery key 206 is operated to the right, While the keys 203, 205, and 207 may be in their normal positions. The circuits are thus arranged for full duplex Working at the substation served by the loops S and. R, a plug 121 being inserted into a jack 122, While a plug 123 may be inserted in a jack 124. Messages may now be sent over leg 101. and other messages received over leg 102 simultaneously. F or the loop 101, the circuit is from negative battery through contacts ot' jack 202, contacts ol key 201 in operated position, conductor 251, right-hand Windings of current meter 110 and relays 105 and 109, conductor 152, contacts oit hey 203 in normal position, conductor 252, inner back contacts of relay 111, conductor 153, contacts of -key 205, conductor 254, lett Winding of relay 113, through the closed loops, and returning to positive battery through the right winding of relay 113.

An open position ot the key 108 disconnects the'circuit through the right Windings of relays 106 and 109, and the armatures of these relays may then move to their spacing contacts under energy in the circuit which extends `from ground through the artificial line resistance 204, normal contacts 'of key 203, Conductor 151, lett Windings ot the relays 100, 10G and meter Y110 to `rrouifided negative battery at the jack 202. llhen the armature o'lI relay 10G leaves its mai-hing; contact the relay lll-ll releases, and over obviousl circuits, ctl`ects response ot a short-circuitiiia vibrator Sill. fr relay :lll may also he under response at this time in disconnecting' the pilot current eipiiiinient as presently n'ill be describml. linflcr operation, the contacts o'l' vibrator Sill set up changes o1l battery current in the primary winding' ot a repeating coil :l0/i. und thue produce an alterimting1 current oil detinite lireipiency as determined by theniechanical and electrical adjustments oll \.'i-- bratoi.' Sli. ln this case, the particular trequeiicy to which the vibrator is adjusted, causes the generation ot an alternating' current olE 'frequency Vthe secondary o1" transtoriner iltll is connected to the line Eli so long' as the armature ot' relay 10G le on its sparing; contact. Alfter traversing; the line lilla the alternating current eilects spouse ot a relay tuned to respond only to the frequency f". llhcu the hay 10F is closed the armature ot the relay llll moves to its inarliii'ig; contati.y thereby disconnectineI the sei'foiulaifl- "Winding` ot the trans 'l'ornier 30.1, and reiiioying the alternating; current troni the line EL.

The relay 331 is el a sloW-to-operate type so that ite armature may remain against iteV baci; contact eo lonfr as relay 10b may he responding; to message impulses, and in turn the relay :lll is ot a sloW-to-release tyje thus insurinzeY that the pilot cnrreiit equipincnt may continue. dircoiinectcd duringmesi-laire sending.

lt n'ill be obvious that each time key 10S is opened to send a spacing signal, the secondary winding ol transformer C301 will he connected to apply the carrier euri-ent to line lGli. lli'hile each time a markingiinpulsc is transmitted, by hey 1.055 being: closed, the armature o'l' relay 10G will be positioned to discoiuiect the. alternatingl current from the line. ln thi@y ay the direct current telegraph impulses are converted into alteruuling` current impulses to control i ant receiving relays.

For convenience in describing` reception on the equipment at Stil, 371, of the sionals i'fioin the lier 10S let it non' be assumed that iuh signals may be under transnii sion 1f 'n the equipments 37T, 30T to be re- Way ol alternatii e* current relay ceired 301 end direct. current relay llQ, in controlline a ree-urine; device or sounder lll. rlflie A t lor this polarized sounder is Alfroin re rroundeil lialteei;riglithandn'iudn ..1 ingr oll`relayv lill, jacli lill, and plug' di sounder lll in the loop il, returi'iinaover the lett-hand Winding` o1. the relay lll?, conduetor ll), lett-hand normal contacts ot key Q07, conductor 25T, contacts ot key 205,

eondi'ietor 258, outer haeltcontaets of relay 1`11 conductor '101i right-hand normal coiitaels ot' key i201', upper contacts oit key i201, conductor 259, armature and marking' contact ol relay 112, coniluctor l5-l, contacts ot hey 2013. to grounded negative battery, by nay ot jacl; 200. lllhen a spacing signal is received over line llfli, the contacts ol relay :lill are opened and relay 112 releases its armature io the spacing contact. Thereupon the positive grounded battery by way olI 'the contacte ol jack 208, is substituted tor the negative battery at jack 20), and thf` sounder lll Will indicate a spacing signal. lior a marking; signal, cessation ot at temi-ating current iii the channel RC1 ot the line lVL, permits restoration ot relaiv Hill. Relay 1li! `then responds to `cloee its inarliii'ie; contacts thereby switching thc loop circuit 11.02 baclr to the negative battery at jack 20th thus causingtlie sounder lll-l to indicate a marking;` sig'rual.

From the foregoiner description it will be clear that signals oi 'if'inatingat the key 100 may control the generation and application ol' alternating current to the line EL, which may be translated by receiving: devices al; equipments 361, ST1.. And further, that in a similar manner7 impulses originating* at Ill?. illli may control the generation and applifation of alternating current impulses to the line lllli whence tlieee impulses may heroine effective through the liull-duplex equipments et Figs. l and 2, and be inanit'ested on the receiver 114i.

1n describiiii;l the operation ol the pilot channel let it nonv be aesumed that all inessage channels ot the line EL may be idle. The respective relays 331, 332, etc., oit the dillercnt channels will therefore stand operated over circuits respectively correspond- 'ing wwith the circuit already described ior the relay 3531. A. hns conductor 352 will thus stand entirely disconnected from grounded battery, lthereby permitting deenerg" :ation olf the slow-torelease relay 341. This closes an obvious circuit for energizing a. shorteircuiting vibrator 342 trom grounded battery in parallel with the primary winding of a transformer 34:3. rlfhe reed armature et this Vibratorfmay be tuned to a `frequency dittering trom the frequencies ot the associated message channels. This vibrator may operate in the saine manner as that already described for the vibrator 311 except that under closure the contacts ot the vibrator short-circuit the primary winding 01E the transformer 3ft-3 in addition to short-cireuiting the Winding of the vibrator.

Such current cl anges .in the trmistormerV Si?) induce alternating current in the secondary winding. Over anobvious circuit which `includes a suitable current indicating device or meter 351 Athese induced currents may reach.. the line circuitEL. At the East station a relay of acceleration type, tuned to respond to the particular frequency ot the pilot current may be present at the point 363, for translating or indicating the presenc-e of this guard current. I'

For convenience in describing the recepti-on of the pilotcurrent let it now be assumed thaty under an idle condition of all message channels on the line WL transmitting pilot equipment'corresponding with the pilot equipment 323 at the lWest oice may be present and under operation at the point373 at the East ollice. At the West oflice a relay 344 of acceleration typesimilar to the relays 304 and 306, but tuned to respond only to the irequency of the pilot current, is connected in bridge of the line WL. Under pilot current this relay responds to disconnect the left-hand winding of a current meter 345, whereupon, current from battery by way of the winding of relay 112 and contacts ci the relay 304l and the rightliand winding of the meter 345 causes a deiiection to the right. This meter may form part of the supervisory equipment of Figs. 1 and'2. The general purpose lof the pilot current 1s to provide a detinite lndicatlon as tothe continuity ot the line and to warnk B41 at the llifvest' o'liice, will stand in its oper-- atedV position in a manner similar to that already described for the latter relay. This serves to disconnect the pilot current equipment, whereupon relay 344 may restore and thus reestablish energy in the left windings ot the meter 345. Assumingnow that the message signals just mentioned may be for the channel RC1, response of the relay 304 will disconnect the Vright winding of the.

meter 345 which may then deflect to the lett under current in the left winding as present by way of the contacts ot the relay 344. f

Each channel may be provided with a 'meter similar o the meter 345 and the con-l tacts of the pilot relay 344 may be connected in common 'to all meters, as indicated, by the conductor in halt-tap from theconductor Ordinarily, however, the pilot current relay may be connected to a. single meter as shown, and in addition to this meter serving Jto-indicate the presence `of message impulses on the associated channel,

it may also indicate the absence of any message signals on the line, and the presence or aiiected by other uses in signal and power systems in connection with which the term pilot current, pilot lamps, etc., may also loe employed.

From the foregoing description, it will be clear that a continuous indication is given ot' the condition of the main lines EL and WL, and of the several receiving channels RC1, RC2, etc., regardless of whether Vmessage signals may be under transmission.

The feature of. the present system which relates to the small amount of signallingk energy required during operation on the channels l, T2, RC3, RC4, etc., renders it possible to use a twofconductor line for transmission in opposite directions without interference or danger of exceeding the limits of the lowv potential levels to which signailing in the telephone plant must he rev stricted.

Referring to Fig. 4, there is shown one arrangement in which a four-conductor line,

. such as, for example the line EL, WL of Fig.

3,may be combined with a ground return Morse system.v rlhe line EL, lVL is preferably duplexed by means of the balancing coils 401 and 402y with their associated artiiicial line networks AL, and AL2 respectively. For this purpose the valancing coil 401 may be inserted at the lVest-oilice in the four-conductor line oi Fig. 3 at the section included wit-hin the dottedv rectangle 374. Similarly, coil 402 at the East otlice may be inserted in the line at the section include-d within the dotted rectangle 375, the lines FL an d 7L now being dispensed with. By means ot this arrangement transmission may be carried on between East and lest otlices by means -ot the two-conductor line ML. Accordingly, alternating current signals impressed on conductors EL as a result of the manipulation of a key similar to key 108 t'ected hy these currents. The currents in line .lili will corres iondina'lv induce currents trom the windings alli' into windings itl ol coil itil. The 'nals thus received over conductors lill. as already noted, may eilect response et the Aproper one ot' the relaysv ilu-l, i306? etc., to cause these signals to he translated into corrcspondingh direct currentv Signals to control receiving equipment as shown in Fins. l and 2.

.te alreadypointed out. the small amount ol2 energy required to actuate the receiving relays i il. SUG. etc.. and their relative unre'pon.-;irencss to current surges render it poi-isihlc to superpose a around return ilorse telegraph system on each conductor et the line rll'i, already duplexed tor alternating; currents. without insertion ot the usual high \'aluc impedances jt'or modifying and #monthincthe direct current impulses.

lte'lierringi' to Figi'. sl a lead 4,05 extends troni the upperniost conductor ot the line circuit ML to a direct current duplex equipment ou" conventional type., while at the opposite end ot' the line a` lead hlill extends trom the same line conductor to duplex equipment :it 1l-23 which may be in duplicate ot the equipment sorted hy the conductor 405. In a correspondine manner leads flOG and 422 conneet other similar direct current equipments to operate in 'full duplex on a` `ground return basis over the lowermostconductor of line lilla -i hey i251 may control a pole changer relay 426 in estahlishiini' changes ot iliolarity to the common or apex; point et the duplex cir uit 'Formed ot a iiiolarixed relay ft2?. the upper winding` o l which is connected through an artificial line AL to earth. while the lower winding is connected over the lead 4:05 to the line conductor. ,Equipment at AE23 under con-- trol of the relay i297 serres for reeeiitien oi signals (n'iginatingr at the distant equipment 423. Sci-called blocking' condensers 129, 430 connected in the main line conductors intermediate the balancing coils 401. J02 and the telegraph branches Ll-(l7 elOG, id21 and 422, serre 'tor continine' the currents of' the direct current' telee'raplisy to the line section ML and excludingy such direct currents from the altennatingr current equipments served hy the lialancine' coils LlOl and 02.

lieretoiorc it has heen necessary to proride positive reactance in the branch leads to the telegraph equipments With additional reactanccs connected to serve as drainage paths `from the main line conductors to earth, in composite Working. lilueh positive reactam es with other negative or capacitive reactances also required in such circuits 'tor delayingl 01 reducing the abruptness ol the rise and fall otl the telegraph impulses have the iurther inulesiral'ile ettect ol appreciahly extendingthe time required 'tor each impulse. This reduces the signalling rate or s-zpeed and therefore lowers the. message capacity ot the direct current circuits. The drainage paths. mentioned also alis'orh or detlect some oi the energy oli the alternating current channels. ln composite working. a phenomenon comg monly referred to as lilcrse thump is present and in general is the result of periodic sur es manifested when a discharge muy rel` snit trom a maximum potential build up or charge harina' heen accunuilated in the networks :termed hy the conniiosite circuits.

ln the present invention advantage is taken oi? the innnunity o!! the acceleration type relays to suhst .ntially the in a abrupt rise and tall of direct current impulses. and also to severe serges in the torni oi Morse thump which may arise in the conn pouitcd circuits. Therefore. as sl'ioun in the drawing` all series. and drainagt-ij or lealiA` reactanct-s hare heen dispensed with as unneecesary and each branch lead 'for the teleeraphie equipineuts comprise a plain conductor suhstaiitially ot zero reactance, as the respective conductors 405, 40G, 2l and Absence ot` the reactances permitsl increase in speed o'l signalling' on the direct current channels and therefore an increase in the message capacity ot these telegraphs.

The importance ot the lilterinc characteristics ofi` the present sensitive receiving' devices ot the alternating' current channels, may he more 'fully realized hy mentioning that ordinarily electrical filters ior excludintr all hut a certain frequency relative to alternating` currents, are usually iiizi.tlt1qttate to exclude the relatively slow moving` Morse. thump surges or iruiluctiii'e etl'ccts arising` in the direct current telegraph channels. Hereto'fore it has therefore heen necessary to suppress such etlects at the source, as hy the indm'tances above mentioned. or to accept the resultincr amount` ot interference on the alternating current portion ot the composited circuits, it has also been diti'icult to protect or salcguarad againsty extraneoun eti'ects due to irregularities in the leads or circuits ol power lines which may parallel the telegraph lines. By comparison` the acceleration type relays ot the present sys tem While ordinarily avoiding; the necessity iior electrical filters are uuatiected hy the Various surge or induetire ellects ahove mentioned. Therefore the acceleration type relays may he Said to serre as translating devices for relaying` impulses in the alter-r natinccurrent channels, While also serving' t.. ini;

as filters in excluding sharp current effects due to high speed direct current working on other channels of the same line, and from extraneous inductive effects.

Fig. 5 shows the kmanner in which a metallic Morse system may be composited with a duplexed line such as ML. The rectangle 501 represents sending and receiving equipment at a Vest oiiice comprising apparatus` similar to that shown in Figs. 1, 2 and 3 as well as a balancing coil such as coil 401. Similarly rectangle 502 represents similar sending and receiving apparatus at an East oilice. Relay 503 is the usual pole changing relay as employed in metallic Morse systems. Relay 504 is a double dit'- erentially wound polarized relay which is neutral to signals transmitted by key 505 but is responsive to incoming signals to affect sounder 424 as well known in the art. Rectangle 506 represents metallic Morse equipment which may be in duplicate of that shown at the lett-hand end of the line in Fig. 5.

In circuits having superimposed metallic direct current telegraphs as distinguished from ground return telegraphs, the poten-y tial ot' the batteries is purposely made low in order to prevent inductive interference. In the present system, however, the filtering ability of the receiving devices. of the alternating current portion of the system substantially avoids this potential limitation and renders it possible to employ batteries of such potentials as may best meet the transmission requirements and further permits greater distances of transmission and less frequent use of' telegraph repeater stations.

The operation of direct current telegraphs .is well understood, therefore, further description of such portions ofthe equipments of Figs. 4 and 5 is believed to be unnecessary.

It may be pointed out that manual type transmitting keys, as 108, 245, 425, 505 and sounders 116, 211, 213, etc. have been shown and described more as a matter of convenience, any or the well vknown forms oit automatic transmitters and receiverswell known in the art may therefore be substituted for the manual equipment in attaining higher transmission speeds'without departing from the present invention. l

From the description given it will be clear that the alternating current relays. of the present system may be readily employedfor repeating signals from a irst to a second line section. The present disclosure is believed to be suiiioient to render this point readily understood without adding further to the drawings. Therefore, let it non7 be assumed that the circuit 7L may constitute a rst line section, working through the equipment at the lVest othce as a repeater station intov a second line section EL tern'iinating at a second or remote station. By inserting a patching cord 115 to join the respective jacks adjacent the jacks 122 and 124 the loop circuit 102 will be connected in series with the loop circuit 101. The key 201 should now be in its operated position for full duplex working ot the terminating ci rcuit. while the battery supply key 206 may be positioned to the right. From the descriptions already given it will be obvious that impulses ot alternating current originating at the transmittingY equipments 367, ST7 may traverse the line L, effect response of the rela which may inturn atleet the relay 12 to set up changes of current polarity in the loop 102. This loop now being patched in series with the loop 101 such changes oit polarity will also become eiiective in the latter loop to .set up responses of the relay 106. Thereupon the current generating vibratcr 311 will respond and permit the relay 100 to apply impulses of alternating current to the line section EL. The receiving equipments 361, 37.1 may respond in translating these impulses. Under this arrangement of the circuits, the loops R and S may continue connected with the loops `101 and 102 and therefore may be said to correspond with intermediate or way stations at which Sounders 114 and 116 may respond under the through signalling just described. At the switchboard point, thepolarized sounder 211 is connected Jrrom the armature of the relay 112 in a so-called leak circuit to ground, while in a corresponding manner the polarized sounder 213 is connected from the armature of the vbreak relay 109 to ground. vTherefore these Sounders may respond to the through impulses for monitoring purposes at the switchboard which may now correspond with a repeater point. lt may be pointed out that under the full du pleaY arrangement of the circuits of Figs. 1 and 2the break relay 109 is without effect except that it may respond in unison with the line relay 106, and control the sounder 213 which is then alonel connected under control or' the break relay.

The line sections WL and EL may be such as commonly employed for telephone circuits and may include the usual types of repeaters such as vacuum tube arrangements for repeating` voice currents. By niieans of patching equipment (not shown) but well understood in the telephone art the equipment of the alternating current telegraphs may be readily patched to circuits which may be employed interchangeably as telephone circuits. This is rendered possible owing to the sensitivity of the acceleration type relays being Such as to vrender them capable of responding to currents of the order and strengths of currents present in the line circuits under speech transmission.

When it may be desired to operate the terininal circuits on the so-called lial'lf-dul'ilex basis the key 201. is placed normal while the battery key 200 may remain in its right hand position. il like settingl ot corresponding switches is made at the duplicate equipment lli-l, ll'l at the distant station.

ln the present,- assuined position ot the switchcs:`y the armature ol relay lli will be comieeteil to the apex oi the polar duplex circuit at the windings ol current meter .1.10, while the spacing contact ot the relay ll' will now be supplied with energy -liroin grounded positive ba'tery by wayl ot jack 208, lower right fontacts olf key 200, condottor 'lain marking' contact and armature ol" break relay 10th coiuluctor 1,5555. contacts ol key 201, thence over conductor 25,0 to

spaci Contact ol this lillest i'ec ;\i\'in gr relay i12. lllnergry lor the marking),l contract oll the relay llt? is now troni negative grounded battery by way ot jaclrtllfl. upper right altornate contacts ol key Q00 and couductor alternating current inuiulses over line llll'i c'li'ecl:` response ot relay ltll. and in turn relay llzl whereby the latter relay may etlect clninees ol' ig-urrent'y polarity at the apex ol' the duplex equipment 'lfornud by the relays '100 and lull. )is well understood in the art` although the net result ot such current changes may be without etitect on these re lays, impulses may however be sety up in the line loops 101 and S the circuits ol" lwhich ha ve already been traced.I to eliect operation ol. the receiving' device l'lt.

Assuininel now that an operator at the latter point may desire to break relative to the incoming` signals, the key 108 may be opened preparatory to sending. This discoi'inection of the loop circuit lOl permits the armatures of the relays 10G and 109 to move to their spacing` contacts. At the break relay 10S) this switches the spacing contact ot the relay 112 troni positive to negative battery thereby renderingl the latter relay inetlcctirc since neeatire battery will now be present on both stops ol this relay lle. .lit this time the spacing' position ol' the relay ltlt cllects release ol" relay flll and response oli the vibrator ll'l to energize the line EL with current at frequency fr. Due to the relay 'llZ harina' been rendered iuel'l'ective by the break relay as just described, impulses arririne' from the lllast' station mayY not be repealed back by the relay ltlt'i over the circuit EL to work the home sounder at the scinliire` operatoi,"s set. 'llhis innnediate silencing4 o'l the latter sounder indicates the presence ot the break signal to the operator originally sending' and therelore it is usual tor the breaking operator to start sending immediately 'following' opening ol the key to establish the break or interruption.

ltinay be pointed out that except ttor the use ot the break relay 109 as described, the

.nition ol the break sional which may only be indicated by mutilation olf the rcturninel signals due to manipulation ol' the key, at the set: where the break signal may have, originated.

litt the switehbtmrd the souridcrs il and 2N serv-e as already described lor indicatintr signals which may be all'cctinsi' the relays llly and 100 respectively. ln association with the sounders a tclefrraph key lo may be employed Yl'or sending i ltancously into the lcleu'raph loops llll and ltl'l. [for this purposc closure ol" a lier 2222 connects grounded battery over the wirmlinp` oli relay lll to ground through the normally closed contacts ol' the key ll. .lis already tiacedr` the le lt run-mal contacts o't thisl relay are in series with the loop lill, whilc the right nornial intacts are in the loop 102. It will tlnrolore be obvious that under control olf the key il?) the relay lll may disconnect and connect the loops l0l and 10i?. to operate the sounders lill` ll-l; and the line relay '100. lu these iuiel'ations the relay lll substitutes lor the relay lli relative to control oilE the loop 102, and also :nibstitutes l'or the lief ltltl in controlling the loop lOl. 'l`he respouses ol thc relay ltltl control transmission ot alternatinfr current impulses over the line lili in a manner similar to that already described. ly operating the key 20T to the right. its lower contacts place a shunt on the lel't normal contacts oil? the relay lll. rthis shuntinol ot the le'lt` contacts ol the relay lll contines control ol this relay to the loop 102, the loop 101 and duplex relay ltlt not then beine4 al'lected by operation ol the key 215. The upper rinht contact lo 'rouo ot the key i207 also translcrs lthe circuit olf the loop 102 troni the armature o'l' the relay ll directly to irronuilcrl ncoatir-e batteri,Y at: the jack 09. thereby disabling` the relay ll'l relative to the present assumed sending' into the loop 102 to work thc sounder ll-l. ,lt will be noted that the alternate contact oi the rio'htshand armature ol the relay lll is connected bv wav ol the lower rie'htcontarts olf kev Q00 directly to po; 'tive battery at the Iiack 209i. This pero s' the rieht armature ol the relay lll to serve as a pole changer in controlline a duplexv equipment which may be patched to the jack llin substitution ol the loop il. Such duplex etpiipn'ient may be in duplicate ol the present; circuits shown in llie l and lllith the key 20T no ioncd to the lclt the loop 102 will be disconnected troni the normal circuits to the relay lili? and connected by way ol the upper rie'lrt contacts oli the key 200 to negative battery at the jack 209. This disables the loop 102 as may be desired in monitoring operations7 or durino: periods the key 201 may be set normal lor half-duplex` operation as already described The key 205 serves with the loop 101 substantially in the saine nn incr as that Ajust described relative tO the ke f 20T and the loop 102. Wvith key 205 to the right the circuit ot the loop 102 is switched from the armature of the relay 111 to the routing previously traced vto the armature of the relay 112. This renders the loop 102 independentof the relay 111 while the key 215 may work the relay 111 in interrupting the loop 101 to affect the sounder 116 and the relay 106 as already described.

`With the key 205 positioned to the lett, the upper transfer contacts switch the line path of the duplex equipment (relays 106 and 109) by way oit' 'the key 206 to positive battery at the jack 208. The middle lett transfer contacts o1 the key 205 switch the loop 101 by way ot the upper right contacts o1 the key 206 to negative battery at the jacl 209, while the lower lett transfer contacts of the key 205 serve the same as the right-hand contacts ot the latter key in switching the loop 102 from control by the relay 111 directly to the cont-rol ot' the relay 112. as already described. The loop 101 will now stand disabled while the relay 111 under control ot the key 215 may effect responses of the relay 106 for sending over the line EL alone as hereinbetore described.

The battery key 206 has two positions so that 1t may serve as a polarity reversing key in connecting battery of either polarity to the marking and spacing contacts of the relays 112 and 109. Then positioned to the left the positive battery at jack 208 is connected to the spacing contact ot the relay 109 and to the marking contactof relay 112, while the negative battery at jack 209 is connected to the marking contact of the relay 109 whence it may vreach the spacing contact of the relay 112. This polarity relation is inverse to that present when the key 206 may be positioned to the right as already described. Other contacts on the key 206 switch the terminals ot the polarized monitoring Sounders 211 and 213 lso that the marking and spacing edects will be in the proper positions for either `polarity of the main batteries.

The key 208 serves for reversing the real line side with the artificial line side of the duplex equipment (relays 106 and 109) and is more particularly for situations where the upper lead of the circuit 101 may be patched to a line conductor formi-ng a ground return circuit at the distant end ot which duplex equipment similar to the equipment of Figs. 1 and 2 may be present. The main battery switch 206 is also concerned in such an arrangement which chiefly a'ttects the polarities of the main line batteries in affording an accumulative effect relative to the energy supplied from the two terminals of a line and also the matter ot the biasing direction of the polar relays in order'that engagement with the spacing and marking contacts of the relays may be in the proper order at both points. For example, assuming that equipment similar to that otFigs. 1 and 2 may be presenty at the East terminal of aground return duplexed line formed of l the upper conductor of the loop 101, the key 206 being positioned to the right, the key 203 normal, the key 201 to the right for full duplex opera-tion and the patching cord115 connected in joining ack 124 with the jack 202, the armature of the relay 112 will thus be connected to the apex o1" the duplex circuit at the meter 110 in substitution of negative battery over the cut-ott contacts of the jack 202. At the iVestpoint, on this assumed line, corresponding key 206 will be positioned to the lett, key 203 operated and key 201 will be operated to the right for full duplex working at the latter point. In this position o13 the circuits the control points of the break relays 109 at each point will be rendered ineffective as already described. rlhe normally closed Vor marking contact of the relay 112 will be energized by negative battery from the jack 209 while the spacing contacts of this relay will be energized from positive battery at the jack 208. Therefore negative grounded battery -will normally be present to the duplex equipment to cont-inne outward over the assumed line. Due to the inverse positions of the switches 206 and 203 at the assumed V7 est otlicea positive grounded battery over the marking Contact and armature ot' a relay corresponding with the relay 112 may flow through the duplex circuit lo line in meeting the negative current from the East otlice. Negative battery will be present on the spacingcontact of the'latter relay while the inverse relation of the windings ot the relay 106 at the lest office due to the operated position of the associated key 203 will correctfor the condition of positive battery normally at the apex of thedupleX equipment. Therefore. correction of bias will thus be established and the armatureor thevrelay v106 at the West orifice will normally stand in proper position on its marking contact.

For the last assumed circuit condition it will be obvious that impulses of alternating current. over the linc LVL may cont-rol the relays 804Y and 112 to repeat directI current impulses into the direct current duplex cir-Y cuit7 whence at the distant assumed Test otlice a relay corresponding with the relay 106 may cont-rol ralternating current equipment similar to the equipment T1 in retranslating the direct current signals into alternating current signals for transmission over al circuit similar to the circuit EL. In a converge 111111111111' 'from ihe "Weet oiiiee i111- pliises may siinuiinneousiy he i111111'eesed over the 'fidi duplex' line to he trzuisdu'fed hei'e from hy Jehe i'einy 1011.

,T11 111:15Y he mentioned that Viov line, 11z1i1'h ing :1s just- 1`leSe1ihe1L ihe 111111111' 1'11111'1111'1111'5 olii the 101.1111 301 :md 10Q 11111 usnniiy 1111 vided -wii'h im'ksl 11111 shown hut Whir'h 111111' he peeeni' 1.11 the hroken AH1111 hoihoi. This eliminates the 2111i Signni i'elnys 'l i131 :1111i i lil from the eh'eiiis 1111111 thus peiehed.

To edil the (111e '1111117 o1' 11111111111' :111111111311111 from 1th@ loop S, operation of' :f1 key 1h01 11111- plieg ground potenti-111 Suhszu'diniijv o A111111', the left-hand vinding' oi the Win11 1.13. Thereupon his diiei'ehiiizd 11311.11' 1e--i11o11dsf to the 111 eiii'i'ent i11 iis: i'iehihmid W11d ing und :ippiies grounded hidiei'y H11-11111111 the Winding of relays 121 :1111i .216 11o ground hr'oilg'h :1 key 21T. The reiey 121 locks i1'- seif 11i1d 1h11 i'einy Q16 independent-1y of ihe l'ehw 113. Response of Velay 2111 dos-es ohvimis eii'euis io euei'grize Sie'md iz111111-1y 21S, 219 11nd :deo 11 Circuit to 'o1111d 1111 nudihie signal 111 i'espondi111514 1o mieh :1 11H the :dieudzmt 11111) 111o111e111i111'i1y depi'eos key 21T io ieiease the relays 121 :1nd 21711 :1 11d iheiehy restore the signals i218, Qi() :1nd 2291 Se? the key Q07 io the left, Close the soviieh Q29 :1nd operate key 215 to Work the sounder 11G :111` already desei'ihed.

)1i i'he Swii'ehh :1rd, key'h Q12 :1nd 2M; i'eSpeeiiveiy serve 'For diseoiuweting the So11i1de1's 211:2 :1nd '213 when desired. jneis 2031 ,209 ,f-ei've for iesiine :1nd puffi-hing: While i'he jocks: i'espeeiivei'v in nssooiziiirm with ineke 12'?. 1111d 1211- 111:1): he pntohed 1o addi'iomd loops equipped similar i'o die loop@ S 11.1111 il. eis'nneeo T72. 174i 11nd e011- deuoei' 173 :1111i ith@ Stm-oud group o1 i111ii1'11' unito Serve ns1` proieeiou against sparking at The 11111111151 oit' he "relays 10.() 11nd lil This i11 f'o11j1111eti1'111 Wiih l'he ilnpedzuioe eoii 'ITi im' 1110diiyi1113 'l'he impuises relative 1o i'he midi-01S of ihese i'eiuys.

i. The 1'1111'1i'1i11111io11 in :1 1010111111111 11.11%1111 olf :1 1'1':111s111i 1;-'=io11 hoe. 111e:111. AF111' Sinudi1111eo111d1' i111111'e1i11g1 (111 smid iine :1 phu'uiil'fy oi :dlei'iming elii'l'eviio of diliereut 'livel quem'iefs. 11 111111 1111de1' eoid'i'oi olf 11109115110 sigmds foi' e111'1'es11o11di11eiy changing; i'he Ch: '111'1'1'1' of Smid ziifm'imiing 1'111'1'e111s, 1'0- eei'fiugg deviees; nfoi' Seid Changed ('111'1'1'11'1@ 11:10h eomprising 11 1311111111011 Het. ood 11 Yihi'zv tory ehi-11d' eonii'oilingf 1111111111111' 'ioi' @111111151- iiig smid 0011111131 Sei. Suid 11'11'111i1e1' heine' adzipied when in vibration io exei'i; e011 11i1111o11r ijv one emwiition oiE eii'euiii control over smid 1111111011 Seix 11nd 1o exert eo11 tinuouiy when :11' rest 21111111101' Condition of ei1'e11i1 r'onii'oi so give rise 11o direct e111'1'e111; iliessa-giye impulses corresponding; i'o said message signals.

Q. The f'o111bi111111i011 i11 11 ieieg'aph system Lesa-eee trol-ling theapplication ot'modulate-d carrierv currents to said line in accordance with direct current message-signals, said'iiiodulated currentsadapted when so appliedy to maintain the associated receiving devices continuous-ly at rest, and means tor controlling the application ofunmodulated car.- rie-r currents to said line in accordance with direct current message. signals, said unmodulated currents adapted to inaiiitainthe associated devices in vibration.

G. Iii aitelegraph system, the combination oit' a line comprising direct! current andv alternating current sections, a vibrator for converting; direct current into alternating,

current in rela-yingsignals betiveen said line sections, .andi an: acceleration type relay Jior translating signals received from saidalteinating current line section.

7; Iii-a'telegraph system, the combination eta line comprising direct current and alterhating; current sections, a vibrator ot the short-circuiting type for converting; dii'ect current into I alternating current in relaying signals between said line sections, and a vibratorytype: relay for translating signals received from said'alternating current line sec-tion.l

8. Y In a: telegraph system, .the combination of a line comprising directv current and alternating current sections, a vibrator-ofthe;

shorteircuiting; type for converting; direct current intoalternating current ini-slayingr sign-als between said line sections, andan acceleration type-'relay for translating sig'- nals--received from said alternating current line section.

9; In a signallingvsystem utilizing signal currentsat loivpotential levelsfor preven-v for producing 'signalling currents, transmittingY devices for applying said currents to said line, and acceleration type relays forv selec-tivelyrcce-iving said currents.

10. In-a system of combined alteriiatingf currenttelegrapliy andtelephony, a line iiicludiiig, repeaters for useV interchangeably ttor speech transmission and'tor telegraphic transmission.V sliort-circuitingvibrators for:

producingsignalling energyv ot the -order of speech currents,- trasnsmittingmeans tor ap.-

plyingsaid:energy to said line for signallino,

aiidf acceleration type relays tor reception ot said energy.

11. In a telegraphsystem, a line provid? ing a plurality of alternating current crlianf nelsaiid af: plurality of direc-t current channels; transmitting. and receiving` equipment' for` each ot said: channels, ,ay sliort-circuiting vibrator for eachalternating current channel Y for producing signalling; energy'tor said i channel, and mea-ns responsive toithe'conditio-n ot. the transmitting` equipment associated-tivitli'analternating'current channel for effec-ting the operation ot" the associated vi- 12. In a telegraph system, tlie'conibination of aline comprising direct current and alternating current secti0nsa short-circuit ing vibrator for supplying carrier current of voice frequency to said .alternating` current circuit, said vibratoirheing normally inert when no messages are being sentover said direct current section, means effective when message impulses are about to be sent over said line for causing said-vibrator to operate to apply carri-er current thereto, means for modulating said carrier-curreiit inl accordance Withk direct current message impulses, and receiving relays for directly convert-ing` the modulated current into coi-- responding direct current message impulses 13. In a system otralternating;currenttelegrapliy, .a plurality ot message channels, a

pilot channel tor said message channels, and

means operative during signal; transmission on any otsaid message channel toi" disabling said pilot channel.

14A- In a system ot Valternating current te-` legraphy. message channels, a pilotA current channel tor said message eliaimels,a source 'ot alternating current and receiving means signals are presenten any ot` said message channels.V

l5.' In a telegraph system, the combination ot' a pluralityot sending channels, a`

main line tor simultaneously propagating messages received'troi-i'i a. plurality o'tf said channels, a source ot ciirre-ntr for piloting` said main line. means tor applying said piloting` current to said line when saidline isidle, and means 'for disconnecting the piloting current from said line when messages' are heilig sent over any ot Said channels.

1G. In a system of alternating current telegiapliy, a line for providing a plurality olii message channels, sources ot alternating currents, transmitting devices for applying said currents to said'line only when signalling thereover, a sourceot pilot current, and means responsive to an. inert condition ol saiddevices for applying said'pilot current to said line.

'17. Ina system otl alternating current ytclegraphy, a line for providing aplurality ot signalling channels, equipment tor a i'irst channel to indicate the` condition ot said line, signalling equipmentfor a plurality of necled with Said main line, a pilot channel and a source ot current therefor, means etil'ectire when :said line is not in use 'for cennecting pilot current thereto to give a coniiinloua indication ot the condition o'li Said line, and means eil'ectire `when any oi said channels are in use lior dieconnecting the pilot current troni eaid line.

itl. In a telegraph system` the combination ot a. main line, message channels connected 1with Said main line, Sourcen ot carrier currenta tor Said mesa ge channels, a pilot cuanw nel and a source o .i fari-ent therefor, means eli'ectirc when said line not in use lor connecting pilot current thereto, and means elf- Atective nhen anyv et said channels are in use vlor replacing said pilot current by a ca frier current.

20. lhe combination in a erstem ot alternating current telegraph;Y ot a main line, telegraph message channels connected with said main line, a pilot channel and a son ce ot current therefor` receiving` mean4 'tor said pilot current comprising a relay lor directlyY converting Said pilot current into a continuous current indication. Said receiving n'ieana being ellectire when the main line is not in uae.

2l. The con'ibination in a ara-lian of alter nating current telegrz phy` oll a main line, a plurality nl niessaige channelf; coinucted with said line a pilot channel .l'or said linci a Shortcircuiting vibrator common to all ot laid ineaaage channele toi: Sippljving pilot current lo Said pilot channel. means eiective. when all ot Said inesage channelsl are idle 'lor renilering Said pilot channel effective to gire a centinuoue iinlication ol the condition olE the main line, and means eiliectire 'when aniv oi Said. channels ie in ure 'for replacing Said pilot current b r carrier current.

i12. ln a telegr: ph System. a line Yfor proriding a plurality ol. alternating current and direct current ineslaure ehannele and a pilot current channel, Said line being energized by signalling energy onl \v when one ot laid meesage channels is in use, aupei-visonv means incuuling indicatorel 'for showing a busi' condition ol" @aid mees-age channels adapted to automaticallj.v energize said pilot current. channel when all oli said message channels are idle` and means 'tor rendering laid pilot current chann l eltective to control a |n'edelermincd one ot aid indicator-S.

if). ln a, tele iph system, a line? a plu rality ot' alternating current n iessage channels, a plu ality ot direct en rent niel'eage channels, and acceleration type rclaxga iter excluding trom Said alternating current channels current effects et Said direct current channels n'ilile translating signals in said alternating` current channels. i

Qi. ln a telegraph eyateni, a line adapted to propagate alternating current telegrai'ih S` rfnale .aiinull'aneousl); in both directions,

means tor impressing Said Signals on Said linel` and nieanfs :tor super-posing on #aid sig nalel uninet-titled high speed direct current telcgral'ih signals, said alternating current :signals and said direct einfrent signals bcing propagated over Said line without mu t: :al in ter terence.

ln a telegraph Syatem, a line :ulapted to propagate alternating current telegraph signals Simultaneously in both directions, means l'or iniprcaning said signals on `Said line.T high Speed direct current telegraph eipiiinnent, and moana cennprising a circuit ol: snbstantialliv zero in'ipedance 'tor operativel",Y associating with `Said line said high Speed equipment whereby unmodil'ied direct current telegraph signal impulses may he inipreeeed on said line without interLlerence with said alternating current signals.

QG. The con'ibination in a telegrz ph Syn tera, olf a main line adapted to siinultaneousla,v propagate alternating current sig* nale and direct current signale without in,d terierenee, a plurility et sending devices :tor impreesing alternating current signal` on .Said line, a plu ality et sending devices Vtor impressing direct current Signals o.V aaid line.` a pluralitaY et receiving devices :tor receiring said direct current signals, and mains coniprising circuits ot low electrical impedance lor operative/liv aarsoc'ating Ieaiel second mentioned sending and receiving devices; with said line.

ifi. .ln a telegraph Syste/n1, a main line adapted to Simultaneouely` propagate alterH nating current Signale and direct current siiginili:7 mann; iter impressing on said line carrier currents `within the voice frequency range, means; tor modifying Said carrier eurrentS in aciairdance with direct current tele graphic signals, and a circuit oit substantiallv zero impedance 'tor associating direct current telegraph signalling' apparatuel with. Said line, whereinv high-Speed Morex signals may he Superposed on Said. inodil'ied eurrentf` Without mutual interjlerence.

E38. lu a telegraph System. a two-conductor line, alternating current duplex telegraph equipment for all'ording a plurality ot' alterhating current signalling channels over Said line, direct current duplex telegraph equip ments connected to each conductor et said line through paths of substantially zero reactance. and acceleration type relays in said alternating current equipments serving as receiving relays to alternating current signais7 said relays being unresponsive to current elliects in said direct current equipments.

Q9. In a teleg faph system, a direct current line sei-tion, duplex sending and receiving telegraphic equipment 'tor said line section, an alternating current line section, duplex signalling equipment for said alternating current line Section, shortcircuiting ribrattn' th'i for producing signalling energy for said alternating current line sections, a second direct current line section, duplex sending and receiving equipment for said second line section, means for translating signals from said direct current line sections into alternating current signals for said alternating current line section, and accelaration type relays for translating signals from the alternating' cui'- i'ent line section into signals for the direct current line sections.

30. Iii a telegraph system, a line providing a plurality of alternating current inessage channels and a plurality of direct current message channels, transmitting and receiving devices for said direct current channels t'or producing signalling impulses of sharp Wave form, transmitting and'receiving devices for said alternating current channels comprising i'ilters formed of acceleration type relays for translating signals in said Y alternating current channels While exclu-ding current eti'ects arising from said sharp Wave signal impulses.

3l. In a telegraph system, a iirst direct current line section, a second direct current line section, duplex telegraph equipments for said line sections, a tWo conductor alternating current line section intermediate said direct current line sections, duplex signalling equipment for said alternating current line section, other direct current duplex telegraph equipment superposed on said alternating current line section by circuits of substantially Zero reactance and forming circuits independent of tlie-irst and second line sections, means for translating signals from the first and second line sections into signals for the alternating current line sections, and acceleration type relays serving as filters in eliminating current eiects of saidy superposed equipments While said relays are trans lating signals from said alternating current line section into said first and said second line sections.

In Witness whereof, I hereunto subscribe my name this 7th day ot August7 A. D., 1925.

HENRY W. ONEILL. 

